Question: Evaluate $5c+cd$ when $c=\dfrac15$ and $d=15$.
Solution: Let's substitute $ c= {\dfrac15}$ and $ d={15}$ into the expression. $\phantom{=}5 {c} + c {d}$ $=5\left( {\dfrac15}\right) +\left({\dfrac15}\right) ({15})$ $=1+3$ $=4$